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Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary

of LockheedMartin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

MELCOR 2.1 Leak Path FactorAssessment and Guidance

David L.Y.Louie

dllouie@sandia.gov

LPF Application of MELCOR

MELCOR is being developed by SNL for the NuclearRegulatory Commission (NRC). Details about thedevelopment of MELCOR from the previous MELCORpresentation were discussed in this workshop .

Even though MELCOR is developed for reactor applications,but because of the modular in nature, a user can selectcertain modules (packages) to be used in LPF applications.

MELCOR is a DOE Toolbox Code for LPF applications

DOE nuclear and nonnuclear facilities for many years

MELCOR 1.8.5 is designated version (which is an obsolete)

Many users have used MELCOR 1.8.6, but requires additionalvalidation and verification procedures

MELCOR 1.8.6 is unsupported by SNL, so that much of the effort canbe devoted to the development of MELCOR 2.0 and beyond.

2

Code Version Differences

FORTRAN language has been used in the life of the MELCORcode development; however, beginning with Version 2.0, theversion of FORTRAN has been switched from FORTRAN77 toFORTRAN95 to ensure future developments in terms ofextensibility and maintainability.

Beginning with Version 2.0, there is a significant change in thecode architecture, even though most the 1.8.6 algorithmswere kept intact.

The original Version 2.0 was developed using the object-orientedapproach in terms of input and calculated variables, which contributesthe input format changes beginning with this version.

Some users may find CVH thermodynamic input difficult touse. To help this, an alternative Input,CV_THERM, restoressome of the Version 1.8.6 features.

5

Assessments

The assessment task is in progress at SNL–

Volume III(Demonstration Problems) of the manual is being developed.

Appendix A of this manual devotes for the non-reactorapplication

This appendix addresses a finding for MELCOR with the gaps analysesconduced by DOE in 2004, which indicated inadequate sampleproblems for LPF specific cases.

Much of the thermal hydraulics and aerosol physical models ofMELCOR are assessed using experiments tailored for reactorapplications.

For LPF applications, we try to verify the MELCOR results from thepreviously reported calculations done, such as those results reportedin the DOE MELCOR guideline report, and other reports, such as fromLA-UR-03-7945 by Jordan and Leonard.

6

MELCOR LPF Results (%)* from MELCOR Guidance Report

TestProblem

Reference Value frominterpolated from(figures) in GuidanceReport

1.8.5

1.8.6

2.1

Appendix C

~8.1 (7-6)

8.13

8.10

8.09

Appendix D

~0.39 (7-12)

0.39

0.39

0.39

Appendix E

~26.3 (7-18)

26.66

26.64

26.63

Appendix F

~0.43 (7-21)

0.43

0.43

0.43

Appendix G

1000 g

100g

10g

1g

~11.58 (7-26)

~12.03 (7-26)

~12.09 (7-26)

~12.09 (7-26)

10.42

10.79

10.83

10.83

10.39

10.75

10.79

10.79

10.38

10.74

10.78

10.78

7

*1.8.5is calculated using the official release version RL, 1.8.6 is calculated using the officialreleaseversionYV 3404, and 2.1 is calculated using revision 1570.

MELCOR Results–Example 3

of LA-UR-03-7945#

8

Case

CrackWidth(mm)

WindSpeed(mph)

SmokeGeneratedby Fire (kg)

HEPA CollectEfficiency (%)

MELCOR LPF Results (fraction)*

1.8.5Reference**

1.8.5

1.8.6

2.1

1

0.5

30

None

99.98

3.9×10-3

3.0×10-3

3.0×10-3

3.0×10-3

2

1

30

None

99.98

9.3×10-3

7.5×10-3

7.5×10-3

7.4×10-3

3

2

30

None

99.98

2.0×10-2

1.7×10-2

1.7×10-2

1.7×10-2

4

5

1

None

99.98

5.1×10-2

4.5×10-2

4.4×10-2

4.4×10-2

5

0.5

10

None

99.98

2.8×10-7

1.2×10-7

2.3×10-7

2.3×10-7

6

0.5

20

None

99.98

1.1×10-4

7.2×10-5

7.6×10-5

7.4×10-5

7

0.5

30

None

99.98

1.0×10-3

9.6×10-4

9.6×10-4

9.3×10-4

8

0.5

30

10

99.98

2.6×10-5

2.8×10-3

2.8×10-3

2.7×10-3

9

0.5

30

25

99.98

1.1×10-5

2.5×10-3

2.5×10-3

2.4×10-3

10

0.5

30

50

99.98

3.9×10-3

2.1×10-3

2.1×10-3

2.0×10-3

11

0.5

30

None

99.95

3.9×10-3

3.0×10-3

3.0×10-3

3.0×10-3

#LA-UR-99-2513 (C. Shaffer and M. Leonard)

*1.8.5 values are using the official release version RL, 186 values are calculated using the official release version YV 3404,

and 2.1 values arecalculated using official release version RL NL 4261.

**1.8.5 reported values from Table 4-2 of LA-UR-03-7945

Useful Features in MELCOR 2.1

Physical Models:

Counter-current flow model (FL_CCF card)–

allows coupling of twopaths through momentum exchange using Epstein-Kentoncorrelations–

mainly for natural circulations

Benchmark againstCFD code

Can be used to address the counter-current exchange of combustiongases through open doorway in a fire scenario

Turbulent aerosol deposition model (RN1_TURB) [optional input]–

models the aerosol deposition in pipes or ducts-the turbulent flowregime. (cautions should be placed when applying this model for theLPF applications, because the benchmark is done for the reactoraccident conditions)